1. Field of the Invention
The present invention relates generally to integrated circuit module packages and assembly methods thereof, and more particularly to radio-frequency (RF) module packages and assembly methods thereof.
2. Description of the Background Art
Mobile phone manufacturers are under competitive pressure to develop smaller, less expensive mobile phones. Accordingly, mobile phone designers may focus on reducing the size and cost of RF module packages in mobile phones. An RF module in a conventional mobile phone includes electronic circuitry for receiving, processing, and transmitting RF signals. The electronic circuitry of the RF module includes both active and passive components. Examples of active components in an RF module include a voltage controlled oscillator, a low noise amplifier, a filter, a mixer, and an antenna. Examples of passive components in an RF module include resistors, capacitors, and inductors.
Typically the active components as well as some smaller passive components of an RF module are integrated into a radio-frequency integrated circuit (RFIC) in the RF module. Generally, larger passive devices are not integrated into the RFIC because the larger passive devices would occupy large areas of the RFIC. In a conventional RF module, for example, an inductor is typically configured in the shape of a spiral in which a coil is wound several times within a defined area on a planar surface of the RFIC. Because the spiral inductor has an inductance proportional to the length of the coil, the number of windings of the coil, and other physical dimensions and geometric properties associated with the coil layout, the spiral inductor may occupy a large area in the RFIC.
An RFIC typically includes one or more power amplifiers that generate a large amount of heat, which may change transistor parameters and affect RF signal processing operation. If the heat generated by the RFIC is not effectively dissipated, electrical components of the RFIC may become damaged and rendered non-operational. Therefore, heat dissipation capacity is an important characteristic of an RF module package in additional to the size and thickness of the RF module package.
FIG. 1 depicts a conventional RF module 100. The conventional RF module 100 includes multiple RFICs 105, 120, and 130 mounted on a lead frame 135. The RFICs 105, 120, and 130 are electrically connected via bonding wires 110 to lead frame inductors 115, 125, and 140 formed on a surface of the lead frame 135. The lead frame inductors 115, 125, and 140 are serpentine inductors composed of the same conductive material as that of the lead frame 135 and are configured to match the impedances of the RFICs 105, 120, and 130. In one type of conventional RF module, the lead frame inductors 115, 125, and 140 may be formed on a printed circuit board (not shown) separate from the lead frame 135. The space occupied by the lead frame inductors 115, 125, and 140 largely determines the size and configuration of the conventional RF module and limits the ability to dissipate heat from the RFICs 105, 120 and 130.
FIG. 2 illustrates a cross-sectional view of the RFIC 105 (FIG. 1) packaged in a conventional plastic ball grid array (PBGA) package 200. As illustrated in FIG. 2, the RFIC 105 is mounted on the lead frame 135, which is attached to a package substrate 210. The package substrate 210 includes vias 215 (e.g., vias 215a-c) that are formed by drilling holes through the package substrate 210. Additionally, solder balls 220 (e.g., solder balls 220a-b) are mounted and electrically coupled to portions of the lead frame 135 near the vias 215. An electrode pad (not shown) of the RFIC 105 is electrically connected to the lead frame inductor 115 via the bonding wire 110a. The via 215c is filled with a conductive filler material, such as a metal, to establish an electrical connection between the lead frame inductor 115 and the portion of the lead frame 135 electrically coupled to the solder ball 220a. 
The PBGA package 200 includes a plastic cap 205 formed over the RFIC 105. Because the lead frame 135 conducts heat much more effectively than the plastic cap 205 and the package substrate 210, heat generated by the RFIC 105 is substantially dissipated in one direction through the lead frame 135 to the ambient air environment of the PBGA package 200. Because the PBGA 200 dissipates heat from the RFIC 105 in substantially one direction, the heat dissipation capacity of the PBGA 200 is limited.
FIG. 3 illustrates a cross sectional-view of the RFIC 105 (FIG. 1) packaged in a thermally enhanced ball grid array (TEBGA) package 300. As illustrated in FIG. 3, the RFIC 105 is mounted on the lead frame 135 (FIG. 1). The lead frame 135 is attached to a front surface 320 of a heat sink plate 310. Electrode pads (not shown) of the RFIC 105 are electrically connected to electrode terminals 340 of a multi-layer printed circuit board (PCB) 325 via bonding wires 110. The electrode terminals 340 are electrically connected to various solder balls 335 through various metal-filled vias 330 in the PCB 325. A heat transfer gel 305 is attached to a back surface 315 of the heat sink plate 310 to facilitate heat transfer from the heat sink plate 310 to the ambient air environment of the TEBGA 300 package. Because heat generated by the RFIC 105 is dissipated in substantially one direction through the lead frame 135, the heat sink plate 310, and heat transfer gel 305, to the ambient air environment of the TEBGA package 300, the heat dissipation capacity of the TEBGA package 300 is limited.
The manufacturing process steps of assembling the multi-layer PCB 325 in the TEBGA package 300 are complex and may result in low product yield. Consequently, the manufacturing cost of a TEBGA package 300 may be higher than that of other types RF module packages. Moreover, the configuration of the multi-layer PCB 325 limits the ability to design a small, thin TEBGA package 300.
It light of the above, there exists a need for a small, thin, RF module package having a high heat dissipation capacity.